1. Field of the Invention
This invention relates to a system for mounting an endless belt/belt sleeve for rotational movement in an endless path around spaced rollers to allow a cutting/grinding operation to be performed thereon and, more particularly, to an apparatus for limiting deviation of the endless belt/belt sleeve from a desired rotational path. The invention is also concerned with the combination of the above system with an apparatus for cutting/grinding the rotating belt/belt sleeve as to make uniform the thickness thereof, define individual belts and/or define ribs in multi-ribbed belts.
2. Background Art
It is known to fabricate power transmission belts, such as multi-ribbed belts, by sequentially building components inside out on a forming drum. More particularly, an outer tension rubber layer, load carrying section and inside compression rubber layer are placed in turn on a forming drum to define a belt sleeve which is thereafter vulcanized. It is also known to rotate an endless sleeve formed by this method on a conforming drum and to define V-shaped grooves in the rotating belt sleeve by means of a grinder having a cutting surface that is complementary to the desired groove configuration in the belt sleeve. An exemplary system of this type is shown in Japanese Patent Publication No. 52-17552.
Multi-ribbed belts are commonly used in drive systems such as serpentine drive systems in automobiles. Typically, one very long belt drives numerous belt components. Since it would be impractical to use a conforming drum to support such a belt/belt sleeve, in that the radius would be unduly large, such belts are commonly formed by training a belt/belt sleeve around spaced rollers having parallel axes. One or both of the rollers are driven to effect rotation of the belt/belt sleeve The belt grooves are formed in the belt/belt sleeve using a grinding wheel similar to that used in forming side edges and grooves in a belt/belt sleeve carried by a forming drum. One of the rollers serves as a backing surface for the grinding wheel.
The above two forming methods are utilized not only on multi-ribbed belts but are also used to define the side surfaces of a conventional V-belt and to separate the individual belts from the belt sleeve using a cutter blade.
The above two techniques are utilized not only in defining individual belt/ribs but also in grinding the back surface of the belt/belt sleeve to produce a uniform thickness for the belt sleeve and the belts ultimately separated therefrom.
Particularly in the latter technique, in order to uniformly produce high quality belts, it is important to limit the deviation of the endless belt/belt sleeve from a predetermined rotational path around the two rollers. This objective is commonly frustrated by the load-carrying cords defining the neutral belt axis. Typically, a plurality of laterally spaced load-carrying cords are embedded in a rubber layer. The individual cords are conventionally made from twisted fibers and naturally bias the belt in a direction that depends on the direction of winding i.e. whether the twisted cords are "S-type" or "Z-type". When an individual belt/belt sleeve is trained around spaced rollers, there is a tendency of the belt/belt sleeve to shift laterally depending upon the twist direction. Further, any inclination of the load-carrying cords can produce the same undesirable result.
The result of the above lateral shifting is that the individual belt dimensions may vary from one to the next. This problem is particularly prevalent using conventional grinding techniques. By such techniques, the grinding wheel is urged against the rotating belt sleeve to cut/grind a portion thereof. Once that portion of the belt sleeve is formed, the grinding structure is retracted and shifted laterally to progressively form the belt sleeve. As long as the grinding wheel or cutter is pressed against the belt sleeve, the lateral shifting is minimized. However, once the cutting/grinding element is retracted fully from the belt sleeve, there is a tendency of the freely rotating belt sleeve to shift laterally as a result of the bias from the load-carrying cords. Further, the cut/ground portion of the belt sleeve become more flexible than the remainder of the belt sleeve which may lead to shifting of the belt sleeve. The result of this is that the width of the belts and/or ribs cut/ground out of the belt sleeve may be irregular.
One proposed solution to the above problem has been to alternatingly wrap "S-type" and "Z-type" load-carrying cords during formation of the belt sleeve. While alternating cords can alleviate the shifting problem to a certain extent, it does not provide a solution in a belt sleeve wherein a cord is continuously wound. The cords are slightly inclined to produce a spiral arrangement which results in a lateral bias on the belt sleeve. In this case, the alternating arrangement of "Z-type" and "S-type" cords does not provide an adequate solution to belt deviation during belt rotation
As an alternative solution, it is known to provide a raised crown on at least one of the rollers in the spaced roller pair The crown surface tends to block lateral shifting of the belt/belt sleeve. However, there is also a tendency of the belt/belt sleeve to bend radially outwardly to conform to the crown surface. The result is deformation of the belt sleeve and the individual belts formed from that part of the belt sleeve adjacent to the laterally opposite edges thereof.